I bought one of these in the early 70s. I'm still using it as I've had no need to upgrade it, and apart from some controls needing a little lubrication once, it has worked perfectly.
It has a multitude of controls onboard, many of which were not available on other amps, like 2 levels of filtering for both treble and base. These controls were designed to make it 'future proof', like possibly being able to record through copyguard records onto cassette tape.
4 years since this thread began, so if you need more info, I'd be happy to pass it on here.
I have photos, instruction manual, specifications, and printed reviews.